Methods and apparatus for retaining a tray stack having a plurality of trays for carrying microelectronic devices

ABSTRACT

Devices and methods for holding a tray stack having a plurality of trays configured to carry and store microelectronic devices. Several devices in accordance with the present invention are particularly applicable to carrying a stack of JEDEC trays that have been loaded with a plurality of microelectronic devices. In one embodiment, the device is a tray retainer including a guide structure configured to allow the tray stack to move in a direction of a load/unload path, and to restrict lateral movement of the tray stack with respect to the load/unload path. The guide structure can have a first end, a second end, and an opening at least proximate to the second end. The guide structure, for example, can have first and second channel sections extending in the direction of the load/unload path. The second channel section can also face the first channel section. The tray retainer can also include a cross-member and a moveable retaining element. The cross-member can extend transverse to the load/unload path at least partially across a first region of the guide structure between the first and second channel sections. The cross-member can be spaced apart from the opening toward the first end of the guide structure. The moveable retaining element is positioned at a second region of the guide structure spaced apart from the cross-member. The retaining element can move between a storage position in which it obstructs the load/unload path and a load/unload position in which it does not obstruct the load/unload path.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional of pending U.S. patent application Ser.No. 09/420,659, filed on Oct. 19, 1999.

TECHNICAL FIELD

The present invention relates to manufacturing microelectronic devices.More particularly, the present invention relates to handling packagedmicroelectronic devices that have been loaded onto JEDEC trays or othertypes of containers.

BACKGROUND

Microelectronic devices can be shipped in a packaged format or anunpackaged format. Packaged microelectronic devices typically include asemiconductor chip, a lead frame, and a protective plastic shell. In oneapplication, the chip has a plurality of bond pads that are electricallycoupled to pins of the lead frame. The chip and the lead frame are thenencapsulated in the plastic shell, and the pins are generally bent intoa desired configuration. Another type of packaged device is a ball gridarray. Unpackaged devices can include CSP (Chip Scale Processing) andKGD (Known Good Die) products in which the chip is not encapsulated in aplastic shell. The packaged and unpackaged devices are typically called“IC devices” or “microelectronic devices.”

During processing of IC devices, a large number of devices are generallyplaced in a tray or other container for protection. JEDEC trays, forexample, are used in the microelectronic device manufacturing industryto hold memory devices and other types of IC devices. JEDEC trays have aplurality of parallel slots to hold several rows of individual ICdevices. The IC devices are often transported between processingmachines or stored in the JEDEC trays. For example, IC devices aretransported between burn-in ovens, electrical testing machines, markingmachines, scanning machines, and the final packaging machines that loadthe IC devices onto shipping trays, continuous tapes or into tubes.

Several JEDEC trays with a large number of IC devices are generallystacked on each other so that a large batch of IC devices can be stored,transported and processed. In one conventional application for handlingJEDEC trays, a disposable band or strap is used to bind several loadedJEDEC trays together and form a tray stack. An empty JEDEC tray is oftenplaced on top of the tray stack to retain the IC devices on the nextlower JEDEC tray. To separate the JEDEC trays for processing or testingthe particular IC devices, the band is cut or otherwise removed from thetray stack. The individual IC devices are then processed. After theindividual IC devices have been processed, they are reloaded onto aJEDEC tray (if they were unloaded), and then the trays are restacked andrebanded into a secure tray stack.

The procedure of banding together a stack of JEDEC trays suffers fromseveral drawbacks. One drawback is that the tray stack can be dropped orjostled before it has been banded. Another drawback is that the bandingmachine may bend or break the trays. Both of these drawbacks typicallyresult in damaging all, or at least some, of the IC devices in the traystack. Still another drawback of banding JEDEC trays together is thatthe banding procedure is time consuming, and it is also cumbersome tostack the banded tray stacks upon each other. A further disadvantage ofbanding JEDEC trays together is that problems arise in tracking the traystacks because identification labels attached to the tray stacks canfall off or be placed on the incorrect tray stacks. Therefore, bandingJEDEC trays together is not a desirable procedure for handling ICdevices.

Another device for handling a stack of JEDEC trays is the Mühlbaurintegrated packaging sleeve or stacker. This device has a base plate andan L-shaped leg projecting from each corner of the base plate. It isexpected that the Mühlbaur sleeve is operated by placing the sleeve overa stack of JEDEC trays such that the base plate contacts the IC devicesin the top JEDEC tray, and then inverting the tray stack and the sleeveso that the JEDEC trays are carried upside down. To load the trays ontoa processing machine, it is thus expected the sleeve is reinverted toright the tray stack, and then the sleeve is removed from the traystack.

Although the Mühlbaur handling sleeve is an improvement over bandingJEDEC trays together, it also suffers from several drawbacks. Oneexpected drawback is that the JEDEC trays can fall out of the sleeve ifit is dropped or tipped over. Another expected drawback of the Mühlbaursleeve is that a JEDEC tray can be removed and lost because the traysare not secured to the sleeve. Therefore, even though the Mühlbaursleeve is an improvement over banding JEDEC trays together, it is alsoexpected to have several drawbacks.

SUMMARY OF THE INVENTION

The present invention relates to devices and methods for holding a traystack having a plurality of trays configured to carry and store packagedmicroelectronic devices. Several devices in accordance with the presentinvention are particularly applicable to carrying a stack of JEDEC traysthat have been loaded with a plurality of packaged microelectronicdevices. In one embodiment, the device is a tray retainer including aguide structure configured to allow the tray stack to move in adirection of a load/unload path, and to restrict lateral movement of thetray stack with respect to the load/unload path. The guide structure canhave a first end, a second end, and an opening at least proximate to thesecond end. The guide structure, for example, can have first and secondchannel sections extending in the direction of the load/unload path. Thesecond channel section can also face the first channel section.

The tray retainer can also include a cross-member and a moveableretaining element. The cross-member can extend transverse to theload/unload path and at least partially across a first region of theguide structure between the first and second channel sections. The term“transverse” in the present disclosure means any non-parallelarrangement and is not limited to only a perpendicular arrangement. Thecross-member can be spaced apart from the opening toward the first endof the guide structure. The moveable retaining element is positioned ata second region of the guide structure spaced apart from thecross-member. The retaining element, for example, can be attached to theguide structure or a long through-pin within the guide structure.

The retaining element can move between a storage position and aload/unload position. In the storage position, the retaining elementprojects transverse to the load/unload path and into the guidestructure. The retaining element obstructs the opening so that loadedtrays cannot be removed from the tray retainer when the retainingelement is in the storage position. In the load/unload position, theretaining element either does not project into the guide structure or itdoes not project as far into the guide structure as it does in thestorage position. When the retaining element is in the load/unloadposition, it does not obstruct the opening so that trays can be loadedor unloaded from the tray retainer.

The tray retainer operates by moving the retaining element between thestorage and the load/unload positions to store, transport or process aplurality of packaged microelectronic devices on a tray stack of JEDECtrays or other types of containers. One embodiment of operating the trayretainer includes moving the retaining element to the load/unloadposition so that the retaining element does not obstruct the load/unloadpath of the guide structure. A plurality of trays in a tray stack arethen inserted into the guide structure by moving the tray stack and/orthe tray retainer along the load/unload path. As the trays are loadedinto the guide structure, the cross-member engages a first end tray atone end of the tray stack. The retaining element is then moved into thestorage position in which it obstructs the load/unload path and contactsa second end tray at an opposite end of the tray stack. In the storageposition, the retaining element and the cross-member restrict the traystack from moving along the load/unload path, and the first and secondchannel sections of the guide structure restrict the tray stack frommoving laterally with respect to the load/unload path. To remove thetray stack from the tray retainer, the retaining element is moved to theload/unload position, and the tray stack and/or the tray retainer ismoved in the opposite direction along the load/unload path.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of a device for retaining a stack of traysin accordance with one embodiment of the invention and a portion of aprocessing machine to which the device can be releasably attached.

FIG. 2 is an exploded isometric view of the device of FIG. 1.

FIG. 3 is an exploded isometric view of a lock/release mechanism inaccordance with an embodiment of the invention.

FIG. 4 is an isometric view partially illustrating a portion of thelock-release mechanism of FIG. 3.

FIG. 5 is a partial cross-sectional view of the lock/release mechanismof FIG. 4 taken along line 5—5 of FIG. 4.

FIG. 6 is a top plan view of a portion of the lock/release mechanism ina released position.

FIG. 7 is a top plan view of the portion of the lock/release mechanismshown in FIG. 6 in a locked position.

FIG. 8A is a partial isometric view of another lock-release mechanism inaccordance with an embodiment of the invention.

FIGS. 8B and 8C are partial cross-sectional views of the lock/releasemechanism of FIG. 8A.

FIG. 9 is a side elevation view of an embodiment of a device forretaining a stack of trays in accordance with another embodiment of theinvention.

FIG. 10 is a cross-sectional view of the device of FIG. 9 taken alongline 10—10.

FIG. 11 is a side elevation view of still another embodiment of a devicefor retaining a stack of trays in accordance with still anotherembodiment of the invention.

FIG. 12 is a cross-sectional view of the device of FIG. 11 taken alongline 12—12.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is generally directed toward tray retainers andmethods for retaining trays that carry and store a plurality of packagedmicroelectronic devices. Many specific details of particular embodimentsof the invention are described below to provide a thorough understandingof such embodiments. The present invention, however, may have additionalembodiments that can be practiced without several of the detailsdescribed in the following description.

FIG. 1 is an isometric view and FIG. 2 is an exploded isometric view ofa tray retainer 20 in accordance with one embodiment of the invention.The tray retainer 20 can retain a tray stack 22 having a plurality ofindividual trays 24 that carry packaged or unpacked IC devices 26. Theindividual trays 24 can be JEDEC trays that have a plurality of slots 27or pockets to receive the IC devices 26. For example, in cases in whichthe IC device 26 has a plurality of pins 28, the slots or pockets 27 canreceive the pins 28.

The tray retainer 20 can also be attached to a processing or testingmachine 30 at a processing station 31. The processing machine 30 caninclude a plurality of fixed mounting elements 32 to engage and hold thetray retainer 20 to the processing station 31. The processing machine 30can also include a plurality of tray singulators 34 having moveable tabs36. The tray singulators 34 extend the moveable tabs 36 to hold a bottomtray of the tray stack 22 over a tray elevator 38 of the processingstation 31. The tray singulators 34 can also retract the moveable tabs36 to drop the bottom tray of the tray stack 22 onto the elevator 38.The tray singulators 34 then extend the moveable tabs 36 to engage andhold the next tray in the tray stack 22 so that only the bottom tray onthe tray elevator 38 is separated from the other trays of the tray stack22. The tray elevator 38 can then move downward to carry the IC devices26 on the separated tray into the processing machine 30. As explained ingreater detail below, the tray retainer 20 securely retains theplurality of trays 24 in the tray stack 22 for storing, transporting orprocessing the IC devices 26.

FIG. 2 illustrates several components of the tray retainer 20 in greaterdetail. The tray retainer 20 can include a casing or guide structure 50configured to (a) allow the tray stack 22 (FIG. 1) to move through theguide structure 50 along a load/unload path P and (b) restrict the traystack 22 from moving laterally with respect to the load/unload path P.This embodiment of the tray retainer 20 further includes a cross-member70 extending across at least a portion of the guide structure 50transverse to the load/unload path P, a plurality of moveable retainingelements 90, and a lock/release mechanism 100. The retaining elements 90and the cross-member 70 can be coupled to the lock-release mechanism 100and/or the guide structure 50. In this embodiment, the lock/releasemechanism 100 moves the retaining elements 90 between a storage positionand a load/unload position. As explained in more detail below, thelock/release mechanism 100 can also simultaneously hold the cross-member70 when the retaining elements 90 are in the storage position, orrelease the cross-member 70 when the retaining elements 90 are in theload/unload position. The tray retainer 20 can securely hold the traystack 22 in the storage position, but allows the tray stack 22 to movealong the path P in the load/unload position. The particular features ofseveral components of this embodiment of the tray retainer 20 will nowbe described in further detail.

The guide structure 50 can have a retaining assembly 52 including afirst end 54 (or first region) and a second end 56 (or second region).In this embodiment, the retaining assembly 52 includes a bearing plate57 and a plurality of L-shaped channel members 58 (identified byreference numbers 58 a-58 d). The retaining assembly 52 can have fewerthan the four L-shaped channel members 58, or the channel members canhave different shapes. The channel members 58 are configured to extendin the direction of the load/unload path P and they define a holdingcavity with a shape corresponding to the profile of the tray stack 22(FIG. 1). In one alternate embodiment (not shown in FIGS. 1 and 2), theretaining assembly 52 has a first C-shaped channel member attached toone end of the bearing plate 57 and a second C-shaped channel memberattached to the opposite end of the bearing plate 57. In anotheralternate embodiment, the retaining assembly 52 can have two diagonallyopposing L-shaped channel members (e.g., channel members 58 a and 58 d,or channel members 58 b and 58 c). The retaining assembly 52 can also bea single four sided box having a rectilinear cross section to receiverectilinear trays, or a cross-section of a different shape correspondingto the shape of different trays. The retaining assembly 52 isaccordingly configured to restrict the tray stack from moving laterallywith respect to the load/unload path P, and to guide the tray stack tomove in the direction of the load/unload path P at appropriate stages ofoperating the tray retainer 20.

The guide structure 50 can be covered by a plurality of panels 62(identified by reference numbers 62 a-62 d). In this particularembodiment, first and second side panels 62 a and 62 b are attached tosides of the retaining assembly 52, and first and second end panels 62 cand 62 d are attached to opposing ends of the retaining assembly 52. Thepanels 62 can be attached to the retaining assembly 52 and to each otherby a plurality of bolts 69 or other suitable fasteners. The retainingassembly 52 and the panels 62 define a housing for containing the traystack. The panels 62 can be a single formed sheet housing, casting ormolding. Additionally, the guide structure 50 and the panels 62 can beformed from a single casting or molding.

The lock/release mechanism 100 can be coupled to the guide structure 50and the cross-member 70 within the housing. FIG. 3 is an explodedisometric view showing selected components of the lock/release mechanism100. Referring to FIGS. 2 and 3 together, the lock/release mechanism 100of this embodiment includes a spring plate 110, an actuator assembly112, a plurality of elongated shafts 120, and a plurality of lockbearings 140 (FIG. 2). Each shaft 120 has a through-pin 122 attached tothe spring plate 110, a sleeve 124 slidably receiving the through-pin122, and a key 128 attached to the through-pin 122. The key 128 is alsoreceived in a slot 126 through the sleeve 124. The sleeves 124 have alower hub 123 received in a bushing 131, and the bushing 131 is receivedin a fixed block 130. The block 130 is attached to one of the first orsecond side panels 62 a (not shown in FIG. 3) or 62 b. The blocks 130accordingly hold the lower section of the sleeves 124 from movingvertically. The through-pins 122 can move axially through the sleeves124 when the spring plate 110 moves vertically to move the retainingelements 90 in the direction of the load/unload path P under the blocks130 (as shown in broken lines). The actuator assembly 112 is rotated inone direction to rotate the through-pins 122, the sleeves 124 and theretaining elements 90 into the storage position (shown in solid lines inFIG. 3) in which the retaining elements 90 project inwardly from theblocks 130 to obstruct the downward motion of the trays. The actuatorassembly 112 can then be rotated 90° in the other direction to rotatethe retaining elements 90 into the load/unload position (shown in brokenlines in FIG. 3) in which the retaining elements 90 do not projectinwardly past the blocks 130 to allow downward movement of the trays.

The actuator assembly 112 can include a drive cylinder 113 (FIG. 3), aplurality of pulleys 132 (FIG. 2) coupled to the through-pins 122, and abelt 134 (FIG. 2) contacting the pulleys 132 and the drive cylinder 113.To operate the actuator assembly 112, a handle 160 (FIG. 2) is insertedinto the drive cylinder 113 and pressed against the spring plate 110 todrive the spring plate 110, the through-pins 122 and the retainingelements 90 downwardly in the direction of the load/unload path P. Thehandle 160 is then rotated 90° to rotate the shafts 120 and theretaining elements 90 between the storage position and the load/unloadposition.

In one particular embodiment, the handle 160 can have a tube 162, aguide-pin 164 projecting from the bottom of the tube 162, and across-pin 166 extending across the tube 162 at an intermediate location.The guide-pin 164 can be inserted into the drive cylinder 113 (FIG. 3)until the lower rim of the tube 162 presses against a bushing 115 (FIG.3) on the spring plate 110 and the cross-pin 166 (FIG. 2) rests in atrough 116 (FIG. 3) of the drive cylinder 113. The handle 160accordingly presses the spring plate 110 downwardly against a pluralityof springs 114 by a distance equal to the distance between the lower rimof the tube 162 and the cross-pin 166. The rotational movement of thehandle 160 rotates the drive cylinder 113 because the cross-pin 166rests in the trough 116 when the handle 160 is fully inserted into theactuator 112. The rotation of the handle 160 moves the belt 134 torotate the pulleys 132, the through-pins 122, the sleeves 124 and theretaining elements 90 between the storage position and the load/unloadposition.

The lock bearings 140 of the lock/release mechanism 100 are attached tothe cross-member 70. Each lock bearing 140 has a hole to slidablyreceive a shaft 120. The rotation of the sleeves 124 relative to thelock bearings 140 also locks and releases the cross-member 70 incoordination with the position of the retaining elements 90. In thisparticular embodiment of the tray retainer 20, the interface between thelock bearings 140 and the sleeves 124 locks the cross-member 70 frommoving along the load/unload path P when the retaining elements 90 arein the storage position. Conversely, when the retaining elements 90 arein the load/unload position, the interface between the lock bearings 140and the sleeves 124 allows the cross-member 70 to move along the shafts120 in the direction of the load/unload path P. As such, thecross-member 70 can be a floating plate that moves upwardly along theload/unload path P as trays are inserted into the tray retainer 20 ordownwardly to drive the trays out of the tray retainer 20 when theretaining elements 90 are in the load/unload position.

The cross-member 70 and the retaining elements 90 also sandwich thetrays 24 (FIG. 1) together in the storage position because thecross-member 70 engages a first end tray at one end of the tray stackand the retaining elements 90 engage a second end tray at the oppositeend of the tray stack. Moreover, because both the cross-member 70 andthe retaining elements 90 are locked against moving along theload/unload path when the retaining elements 90 are in the storageposition, the cross-member 70 and the retaining elements 90 prevent thesandwiched tray stack from moving along the load/unload path. The trayretainer 20, therefore, can securely hold tray stacks having differentnumbers of trays for storage and transportation, and then quicklyrelease the tray stack for easy loading/unloading at a processingmachine.

The operation of the tray retainer 20 and the processing machine 30 arebest understood by referring to FIGS. 1 and 2. The tray stack 22 isinitially loaded into the tray retainer 20 by engaging the handle 160with the actuator assembly 112 and rotating the handle 160 to move theretaining elements 90 into the load/unload position. The tray stack 22is then inserted into the guide structure 50. The cross-member 70 slidesalong the shafts 120 as the tray stack 22 moves into the guide structure50. After the trays are loaded into the guide structure 50, the handle160 is rotated to move the retaining elements 90 into the storageposition and to lock the cross-member 70 from moving axially along theshafts 120. The loaded tray retainer 20 is then stored or transported toa processing machine.

To remove individual trays 24 from the tray container 20 at theprocessing machine 30, the tray container 20 is placed onto theprocessing station 31. The handle 160 is reinserted into the actuatorassembly 112 and rotated to move the retaining elements 90 from thestorage position into the load/unload position. In this embodiment, whenthe guide elements 90 are in load/unload position, they also engage themounting elements 32 at the processing station 31 to releasably hold thetray retainer 20 to the processing machine 30. The tray singulators 34then separate the lower most tray 24 of the tray stack 22 and place iton the tray elevator 38. The trays 24 are accordingly unloaded from thetray retainer 20 to process the IC devices 26 in the processing machine30. The processing machine 30 can also have a second processing station(not shown) with an empty tray retainer 20 to receive trays that havebeen reloaded with the processed package devices 26. Therefore, theprocessing machine 30 can have an input processing station with one trayretainer 20 and an output processing station with another tray retainer20. After the trays 24 have been loaded into a tray retainer 20 at theoutput station, the handle 160 is rotated to move the retaining elements90 into the storage position and to disengage the retaining elements 90from the mounting elements 32. The loaded tray retainer 20 is thenremoved from the processing machine 30.

The embodiments of the tray retainer 20 shown in FIGS. 1-3 selectivelyhold the trays within the guide assembly 50 to prevent both axial andtransverse movement with respect to the direction of the load/unloadpath P. As such, JEDEC trays 24 in a tray stack 22 cannot fall out ofthe tray retainer 20 or be separated from one another. The tray retainer20 can even be dropped or jostled without damaging the JEDEC trays 24 orthe IC devices 26. Therefore, the particular embodiments of the trayretainer 20 shown in FIGS. 1-3 are expected to reduce losses of ICdevices caused by accidents.

The particular embodiments of the tray retainer 20 shown in FIGS. 1-3can also be stacked upon one another to securely and efficiently store alarge number of IC devices. Referring to FIG. 1, the panels 62 can eachhave a rim 64 projecting upwardly from their upper edges and a slot 66extending along their lower edges. The rim 64 receives the slot 66 of animmediately adjacent upper tray retainer 20. The bottom of one trayretainer 20 can thus be stacked on top of a lower tray retainer 20. Inanother embodiment, the rim 64 can extend around a portion of the sideof panel 62 a and project away from the flat face of panel 62 a, and theslot 66 can extend around a portion of panel 62 b. One tray retainer 20can thus be stacked on top of a side panel 62 a of a lower trayretainer. The tray retainers 20 can thus be stacked vertically intop/bottom or side/side arrangements. The particular embodiments of thetray retainer 20 illustrated in FIGS. 1-3 can accordingly be stacked ontop of and/or beside one another to efficiently store a large number ofloaded or empty tray retainers 20.

The particular embodiments of the tray retainer 20 illustrated in FIGS.1 and 2 can also allow movement along the load/unload path P only whenthe tray retainer 20 is mounted to the processing station 31 of theprocessing machine 30. One feature of these particular embodiments isthat the retaining elements 90 engage the fixed mounting elements 32 atthe processing station 31 and do not obstruct the tray stack 22 frommoving along the load/unload path P when the retaining elements 90 arein the load/unload position. The tray retainer 20 is accordinglysecurely mounted to the processing station 31 at all times during whichthe retaining elements 90 are in the load/unload position. Therefore,the particular embodiments of the tray retainer 20 illustrated in FIGS.1 and 2 are expected to inhibit the inadvertent removal of trays fromthe tray retainer 20.

In light of the foregoing embodiments of tray retainers, particularembodiments of the lock bearing 140 and the sleeve 124 will now bedescribed. FIG. 4 is an isometric view and FIG. 5 is a cross-sectionalisometric view of one embodiment of the lock bearing 140 and the sleeve124. The sleeve 124 can have an axial bore 125, outer sections 127(identified by reference numbers 127 a and 127 b), and flat sections129. Referring to FIG. 5, the sleeve 124 is received in an axial hole142 of the lock bearing 140, and the through-pin 122 is received in thebore 125 of the sleeve 124. The lock bearing 140 also includes grooves144, resilient engagement elements 146 received in the grooves 144, andan annular shoulder 148. Each lock bearing 140 can be attached to aplate or other structure (e.g., the cross-member 70) by a plurality ofscrews (not shown) that engage the annular shoulder 148. In operation,the sleeve 124 rotates with respect to the lock bearing 140 so that theouter sections 127 contact opposing sides of the engagement elements 146for holding the cross-member 70, or so that the flat sections 129 facethe engagement elements 146 to space the sleeve 124 apart from theengagement elements 146 for sliding the lock bearings 140 along thesleeve 124. The lock bearing 140 can be formed integrally with thecross-member 70.

FIGS. 6 and 7 are top plan views of the operation of this embodiment ofthe sleeves 124 and the lock bearings 140. FIG. 6, more specifically,illustrates the sleeves 124 in the released position such that the flatsections 129 are spaced apart from contact sections 147 of theengagement elements 146. The outer sections 127 of the sleeve 124 cancontact the wall of the hole 142 such that the lock bearing 140 slidesalong the curved surfaces of the outer sections 127. FIG. 7 illustratesthe sleeves 124 in the locked position after they have been rotated 90°so that the outer sections 127 contact the contact surfaces 147 of theengagement elements 146. The frictional contact between the outersections 127 and the flexible engagement elements 146 accordinglyprevents the cross-member 70 from moving axially along the sleeves 124.

The lock bearing 140 and the sleeve 124 can have differentconfigurations or be used on different machines. The lock bearing 140and sleeve 124, for example, can be used in virtually any application inwhich a plate or other member moves along a rod, shaft or rail. Also,the lock bearing 140 and sleeve 124 can have other configurations inwhich the lock bearing 140 rotates relative to the sleeve 124, or inwhich rotation of more or less than 90° is sufficient to lock or releasethese components

FIGS. 8A-8C illustrate another embodiment of a sleeve 224 and a lockbearing 240. In this embodiment, the sleeve 224 has an axial bore 225, aflat section 229, and a plurality of truncated annular teeth 227 spacedapart from one another along the length of the sleeve 224. The lockbearing 240 has an axial hole 242 through which the sleeve 224 isreceived, a flat portion 243, and a slot 244 in the flat portion 243. Asshown by FIG. 8B, the flat section 229 of the shaft 224 faces the flatportion 243 of the lock bearing 240 in an unlocked position to allow thelock bearing 240 to slide along the shaft 224. FIG. 8C illustrates theshaft 224 and the lock bearing 240 after the shaft 224 has been rotatedby 90°. As shown in FIG. 8C, at least one of the truncated annular teeth227 is received in the slot 244 to prevent the lock bearing 240 frommoving axially along the shaft 224.

The tray retainer can also have embodiments that are different from theembodiments of the tray retainer 20 described above with reference toFIGS. 1-3. For example, FIG. 9 is a side elevation view and FIG. 10 is across-sectional view along line 10—10 of FIG. 9 illustrating a trayretainer 300 in accordance with another embodiment of the invention. Thetray retainer 300 can include a guide structure or casing 350 having atray retaining assembly with a first channel section 352 a and a secondchannel section 352 b facing the first channel 352 a. The first andsecond channel sections 352 a and 352 b can extend in the direction ofthe load/unload path P. The tray retainer 300 further includes across-member 370 extending transverse to the load/unload path P. Thecross-member 370 generally extends at least partially across a firstregion 351 of the guide structure 350 between the first and secondchannel sections 352 a and 352 b. The cross-member 370 accordinglyprevents trays from moving axially along the load/unload path P beyondthe first region 351 of the guide structure 350.

The tray retainer 300 can also include a moveable retaining element 390positioned at a second region 353 of the guide structure 350. The secondregion 353 of the guide structure 350 is spaced apart from the firstregion 351 such that the retaining elements 390 are spaced apart fromthe cross-member 370 by a distance equal to a desired height of a traystack. In this particular embodiment, the moveable retaining element 390is pivotally attached to each of the first and second channel sections352 a and 352 b. The first and second regions 351 and 353 of the guidestructure 350 can accordingly be at locations other than the ends of theguide structure 350.

The moveable retaining elements 390 are moveable from a load/unloadposition (shown in solid lines) to a storage position (shown in brokenlines). In the load/unload position, the retaining elements 390 eitherdo not project into a cavity 360 of the guide structure 350, or theretaining elements 390 merely do not project as far into the cavity 360as they do in the storage position. In either case, a tray stack can bemoved axially in the direction of the load/unload path P to slide traysinto or out of the tray retainer 300 when the retaining elements 390 arein the load/unload position. In the storage position, the retainingelements 390 project transverse to the load/unload path P and into thecavity to hold the tray stack between the retaining elements 390 and thecross-member 370.

FIGS. 11 and 12 illustrate a tray retainer 300 a in accordance withanother embodiment of the invention. In this embodiment, the trayretainer 300 a has a unitary guide structure 350. The first channelsection 352 a is defined by one portion of the guide structure, and thesecond channel section 352 b is defined by an opposing side of the guidestructure. The guide structure 350 can be a four-sided box having endwalls 354 a and 354 b, and side walls 356 a and 356 b. The retainingmembers 390 can be attached to the guide structure 350 at each end wall354 a and 354 b, or at each side wall 356 a or 356 b.

Although the foregoing sets forth specific embodiments of the invention,it will be appreciated that various modifications may be made to thespecific embodiments described above without deviating from the spiritand scope of the invention. The specific embodiments described aboveprovide sufficient information to enable a person skilled in the art tomake and use the best modes of the invention, but the claims are notlimited to the particular embodiments described above. Accordingly, theinvention is not limited except as by the appended claims.

1. A tray retainer for holding a tray stack having a plurality of traysthat are configured to carry microelectronic devices, comprising: aguide structure having a first region, a second region spaced apart fromthe first region, a first channel section extending in a direction of aload/unload path between the first and second regions, and a secondchannel section extending in the direction of the load/unload pathbetween the first and second regions, the second channel section facingthe first channel section; a cross-member extending transverse to theload/unload path and at least partially across the first region of theguide structure between the first and second channel sections; and amoveable retaining element positioned at the second region of the guidestructure, the retaining element being moveable to a storage position inwhich the retaining element projects a first distance transverse to theload/unload path into the second region of the guide structure, and theretaining element being moveable to a load/unload position in which theretaining element either does not project into the second region of theguide structure or projects a second distance less than the firstdistance, wherein when the tray retainer holds the tray stack and theretaining element is in the storage position, the cross-member contactsa tray at one end of the tray stack and the retaining element contacts atray at the opposite end of the tray stack.
 2. The tray retainer ofclaim 1 wherein: the guide structure comprises a frame having a bearingplate with a first end and a second end, a plurality of elongatedL-shaped channel members attached to the first and second ends of thebearing plate, and panels attached to at least one of the channelmembers and the bearing plate, the channel members including first andsecond channel members attached to the first end of the bearing platedefining the first channel section and third and fourth channel membersattached to the second end of the bearing plate defining the secondchannel section, wherein the channel members project from the bearingplate in the direction of the load/unload path, and wherein the firstchannel member faces the third channel member and the second channelmember faces the fourth channel member; the tray retainer furtherincludes a lock/release mechanism coupled to the guide structure, thecross-member and the retaining element, the lock/release mechanismincluding at least one shaft coupled to the retaining element, anactuator coupled to the shaft, and a lock bearing coupled to thecross-member, the shaft having a sleeve with a contact portion, a boreand a slot, and the shaft also having a through-pin slidably received inthe bore of the sleeve, and the shaft further having a key attached tothe through-pin and received in the slot of the sleeve, the key rotatingthe sleeve with rotation of the through-pin, the actuator having apulley attached to one end of the though pin, a drive cylinder and abelt engaging the drive cylinder and the pulley, and the lock bearinghaving a resilient engagement member to selectively engage the contactportion of the sleeve, wherein an operator rotates the drive shaft torotate the through-pin, sleeve and retaining element between the storageposition and the load/unload position; and the cross-member comprises amoveable plate.
 3. The tray retainer of claim 1 wherein the guidestructure comprises a frame having a bearing plate with a first end anda second end, a plurality of elongated L-shaped channel members attachedto the first and second ends of the bearing plate, and panels attachedto at least one of the channel members and the bearing plate, thechannel members including first and second channel members attached tothe first end of the bearing plate defining the first channel sectionand third and fourth channel members attached to the second end of thebearing plate defining the second channel section, wherein the channelmembers project from the bearing plate in the direction of theload/unload path, and wherein the first channel member faces the thirdchannel member and the second channel member faces the fourth channelmember.
 4. The tray retainer of claim 1 wherein: the first channelsection comprises a first C-shaped channel member, and the secondchannel section comprises a second C-shaped channel member; and thecross-member comprises a plate having a first end attached to the firstC-shaped channel member and a second end attached to the second C-shapedchannel member.
 5. The tray retainer of claim 1 wherein: the firstchannel section comprises a first C-shaped channel member, and thesecond channel section comprises a second C-shaped channel member; thecross-member comprises a floating plate extending at least partiallybetween the first C-shaped channel member and the second C-shapedchannel member, the floating plate being moveable along the load/unloadpath; and the retaining element comprises a tab projecting into a cavitybetween the first and second C-shaped channel members in the storageposition.
 6. The tray retainer of claim 1 wherein: the first channelsection comprises first and second L-shaped channel members, and thesecond channel section comprises third and fourth L-shaped channelmembers; and the cross-member comprises a plate having a first endattached to the first and second L-shaped channel members and a secondend attached to the third and fourth L-shaped channel members.
 7. Thetray retainer of claim 1 wherein: the first channel section comprisesfirst and second L-shaped channel members, and the second channelsection comprises third and fourth L-shaped channel members; thecross-member comprises a floating plate extending at least partiallybetween the first L-shaped channel member) the second L-shaped channelmember, the third L-shaped channel member, and the fourth L-shapedchannel member, the floating plate being moveable along the load/unloadpath; and the retaining element comprises a tab projecting into a cavitybetween the first and second L-shaped channel members in the storageposition.
 8. The tray retainer of claim 1 wherein: the guide structurecomprises a unitary shell, and the first channel section is defined by afirst end of the shell and the second channel section is defined by asecond end of the shell; and the cross-member comprises a plate attachedto the shell.
 9. The tray retainer of claim 1, further comprising alock/release mechanism having an actuator, a shaft having a first endcoupled to the retaining element and a second end coupled to theactuator, and a lock bearing attached to the cross-member and slidablyreceiving the shaft, the actuator rotating to rotate the retainingelement between the storage position and the load/unload position and torotate the shaft between a lock position and a release position relativeto the lock bearing, the lock bearing preventing the cross-member frommoving along the shaft when the shaft is in the lock position and theretaining element is in the storage position, and the lock bearingallowing the cross-member to move along the shaft when the shaft is inthe release position and the retaining element is in the load/unloadposition.
 10. The tray retainer of claim 1, further comprising alock/release mechanism having an actuator and a shaft coupled to theactuator, the actuator having a drive cylinder and a belt contacting thedrive cylinder, and the shaft having a through-pin including a first endcoupled to the belt and a second end attached to the retaining element,a key attached to the through-pin proximate to the second end, and asleeve having a bore receiving the through-pin and a slot receiving thekey, wherein rotation of the drive cylinder rotates the through-pin andthe sleeve to move the shaft between a lock position in which theretaining element is in the storage position and a release position inwhich the retaining element is in the load/unload position.
 11. The trayretainer of claim 1 wherein: the guide structure comprises a framehaving a bearing plate and a plurality of channel members including atleast a first channel member projecting from one end of the bearingplate and a second channel member projecting from another end of thebearing plate, the first channel member defining the first channelsection of the guide structure and the second channel member definingthe second channel section of the guide structure; the retaining elementcomprises a tab; and the tray retainer further comprising a lock/releasemechanism having an actuator, a shaft coupled to the actuator, and alock bearing slidably receiving the shaft and attached to thecross-member, wherein movement of the actuator to a first position movesshaft to a lock position in which the lock bearing engages the shaft toprevent the cross-member from moving along the shaft and in which thetab projects into a space between the first and second channel membersin the storage position, and wherein movement of the actuator to asecond position moves the shaft to a release position in which lockbearing disengages the shaft to allow the cross-member to move along theshaft and in which the tab is at least partially removed from the spacebetween the first and second channel members in the load/unloadposition.
 12. The tray retainer of claim 1, further comprising alock/release assembly including: a lock bearing attached to thecross-member, the lock bearing having a hole; a shaft extending in thedirection of the load/unload path, the shaft being slidably androtatably received in the hole of the lock bearing, wherein at least oneof the lock bearing and the shaft rotates between a lock position and arelease position; and an engagement assembly having an engagementelement, a contact surface and a release surface, the engagement elementbeing coupled to one of the shaft or the lock bearing, and the contactsurface and the release surface being on the other of the shaft or thelock bearing, the contact surface being configured to contact theengagement element and prevent axial movement between the lock bearingand the shaft in the lock position, and the release surface beingconfigured to be spaced apart from the engagement element and allowaxial movement between the lock bearing and the shaft in the releaseposition.
 13. The tray retainer of claim 12 wherein: the shaft comprisesa contoured elongated member having a flat section defining the releasesurface and a rounded outer section defining the contact surface, therounded outer section having a curved outer surface with a diameter tofit within the hole of the lock bearing; and the lock bearing comprisesa hub having a cylindrical hole, an interior groove with in the hole,and a resilient member defining the engagement member in the groove, theflat section being juxtaposed to the resilient member in the releaseposition and the outer section contacting the resilient member in thelock position.
 14. The tray retainer of claim 12 wherein: the shaftcomprises an elongated member having a flat section defining the releasesurface and a plurality of truncated annular teeth defining the contactsurface; and the lock bearing comprises a hub having a cylindrical hole,a flat portion, and a slot in the flat portion defining the engagementelement, the flat section of the shaft being juxtaposed to the flatportion of the lock bearing in the release position and at least one ofthe annular teeth being in the slot in the lock position.
 15. A retainerfor holding a tray stack having a plurality of trays configured to carrya plurality of microelectronic devices, comprising: a casing having aguide structure with a first end, a second end, an interior holdingarea, and an opening at the second end of the guide structure forreceiving the trays, the guide structure being configured to receive thetray stack and allow the tray stack to move along a load/unload paththrough the guide structure; a cross-member member extending across atleast a portion of the casing transverse to the load/unload path, thecross-member being spaced apart from the second end of the casing; and aplurality of moveable retaining elements at least proximate to thesecond end, the retaining elements being moveable between a storageposition in which the retaining elements project into the interiorholding area of the guide structure to obstruct the load/unload path,and the retaining elements being moveable into a load/unload position inwhich the retaining elements are clear of the load/unload path, whereinwhen the retainer holds the tray stack and the retaining elements are inthe storage position, the cross-member and the retaining elements holdthe tray stack and inhibit movement of the tray stack along theload/unload path.
 16. The retainer of claim 15 wherein: the guidestructure has a first channel section comprising a first C-shapedchannel member and a second channel section comprising second C-shapedchannel member; and the cross-member comprises a plate having a firstend attached to the first C-shaped channel member and a second endattached to the second C-shaped channel member.
 17. The retainer ofclaim 15 wherein: the guide structure has a first channel sectioncomprising a first C-shaped channel member and a second channel sectioncomprising a second C-shaped channel member; the cross-member comprisesa floating plate extending at least partially between the first C-shapedchannel member and the second C-shaped channel member, the floatingplate being moveable along the load/unload path; and the retainingelement comprises a tab projecting into a cavity between the first andsecond C-shaped channel members in the storage position.
 18. Theretainer of claim 15 wherein: the guide structure has a first channelsection comprising first and second L-shaped channel members and asecond channel section comprising third and fourth L-shaped channelmembers; and the cross-member comprises a plate having a first endattached to the first and second L-shaped channel members and a secondend attached to the third and fourth L-shaped channel members.
 19. Theretainer of claim 15 wherein: the guide structure has a first channelsection comprising first and second L-shaped channel members and asecond channel section comprising third and fourth L-shaped channelmembers; the cross-member comprises a floating plate extending at leastpartially between the first L-shaped channel member, the second L-shapedchannel member, the third L-shaped channel member, and the fourthL-shaped channel member, the floating plate being moveable along theload/unload path; and the retaining element comprises a tab projectinginto a cavity between the first and second L-shaped channel members inthe storage position.
 20. The retainer of claim 15, further comprising alock/release assembly including: a lock bearing attached to thecross-member, the lock bearing having a hole; a shaft extending in thedirection of the load/unload path, the shaft being slidably androtatably received in the hole of the lock bearing, wherein at least oneof the lock bearing and the shaft rotates between a lock position and arelease position; and an engagement assembly having an engagementelement, a contact surface and a release surface, the engagement elementbeing coupled to one of the shaft or the lock bearing, and the contactsurface and the release surface being on the other of the shaft or thelock bearing, the contact surface being configured to contact theengagement element and prevent axial movement between the lock bearingand the shaft in the lock position, and the release surface beingconfigured to be spaced apart from the engagement element and allowaxial movement between the lock bearing and the shaft in the releaseposition.
 21. A retainer for holding a tray stack having a plurality oftrays that are configured to carry microelectronic devices, comprising:a protective casing including a guide structure having a first guidesection configured to receive a first side of the tray stack, a secondguide section configured to receive a second side of the tray stack, thefirst and second guide sections defining an opening and an interiorholding area configured to retain the tray stack in a stackedarrangement and to allow the tray stack to move through the guidestructure; a cross-member extending at least partially between the firstand second guide sections; and a plurality of moveable retainingelements in the casing at least proximate to the opening, the retainingelements being moveable between a storage position in which theretaining elements project into the opening and a load/unload positionin which the retaining elements either do not project as far into theopening or are completely removed from the opening, wherein when theretainer holds the tray stack and the retaining elements are in thestorage position, the cross-member supports one end of the tray stackand the retaining elements support the opposite end of the tray stack.22. The retainer of claim 21 wherein: the first channel sectioncomprises a first C-shaped channel member, and the second channelsection comprises a second C-shaped channel member; and the cross-membercomprises a plate having a first end attached to the first C-shapedchannel member and a second end attached to the second C-shaped channelmember.
 23. The retainer of claim 21 wherein: the first channel sectioncomprises first and second L-shaped channel members, and the secondchannel section comprises third and fourth L-shaped channel members; andthe cross-member comprises a plate having a first end attached to thefirst and second L-shaped channel members and a second end attached tothe third and fourth L-shaped channel members.
 24. The retainer of claim21, further comprising a lock/release assembly including: a lock bearingattached to the cross-member, the lock bearing having a hole; a shaftextending in the direction of the load/unload path, the shaft beingslidably and rotatably received in the hole of the lock bearing, whereinat least one of the lock bearing and the shaft rotates between a lockposition and a release position; and an engagement assembly having anengagement element, a contact surface and a release surface, theengagement element being coupled to one of the shaft or the lockbearing, and the contact surface and the release surface being on theother of the shaft or the lock bearing, the contact surface beingconfigured to contact the engagement element and prevent axial movementbetween the lock bearing and the shaft in the lock position, and therelease surface being configured to be spaced apart from the engagementelement and allow axial movement between the lock bearing and the shaftin the release position.